Using a straightforward systems approach, this book explores the inner workings of the complex, modern U.S. public health system--what it is, what it does, how it works, and why it is important. The book covers the origins and development of the modern pubic health system; the relationship of public health to the overall health system; how the system is organized at the federal, state, and local levels; its core functions and how well these are currently being addressed; evidence-based practice and an approach to program planning and evaluation for public health interventions; public health activities such as epidemiological investigation, biomedical research, environmental assessment, policy development, and more.